Recently, a new communication method has been developed. The communication method uses a high-frequency electromagnetic wave referred to as a millimeter wave to increase the communication speed of wireless communication. The millimeter wave is regarded to have a wavelength of 10 to 1 mm and a frequency of 30 to 300 GHz so that a channel can be allocated in, for example, 60 GHz band by the GHz unit.
Generally, the millimeter wave has characteristics of more strongly traveling in a straight line and having a return loss larger than a microwave. Thus, a wireless communication pathway in a millimeter wave communication is mainly a direct wave or a wave reflected around once. Further, the millimeter wave has a characteristic of having a large free space propagation loss (a short reach of radio wave). Thus, in the case of performing wireless communication using the millimeter wave, while there is an advantage, in comparison with a case where the microwave is used, that the space is easy to divide, the communication distance will be shorter.
To compensate such a disadvantage of the millimeter wave in order to use a high-speed wireless communication using the millimeter wave in more situations, it is considered that the antennas of a transmitting apparatus and a receiving apparatus have directionalities and each of the transmission beam and the reception beam is directed toward the correspondent so that the communication distance is increased. The directionalities of the beams can be controlled, for example, by changing the weights of a plurality of antennas provided in each of the transmitting apparatus and the receiving apparatus. For example, Patent Literature 1 mentioned below discloses a technique for performing wireless communication with a millimeter wave by exchanging a control signal in advance using a communication medium such as a sound wave, an infrared ray, or a light to learn an optimal directionality of the antenna.